The present invention relates to magnetic resonance systems. It finds particular application in conjunction with magnetic resonance systems for imaging a patient's spinal column and will be described with particular reference thereto. However, it is to be appreciated that the invention will also find application in conjunction with imaging other areas of a human or non-human subject, spectroscopically analyzing regions of a subject, and the like.
Conventionally, large, patient encircling whole body coils are utilized when imaging large areas of a patient. When imaging a limited, specific region of the patient, a single surface coil is commonly utilized to receive signals from a smaller the region of interest. The single surface coil may have multiple elements, all of which are active and work concurrently as a single receiving coil.
Various techniques have been developed which take advantage of a surface coil's sensitivity to only a small region when imaging larger regions. In one technique illustrated in "Coil Holder and Marker System for MR Imaging of the Total Spine", Abrahams, et al., Radiology, Volume 172, No. 3, pages 869-871, Sep. 1989, the surface coil was physically moved from location to location. This enabled each image slice to be positioned appropriately within the field of view of the surface coil.
In the technique illustrated in "Parallel Image Acquisition from Non-Interacting Local Coils", Hyde, et al., Journal of Magnetic Resonance, Volume 70, pages 512-517, 1986, two surface coils were active concurrently and their outputs combined. One disadvantage of this technique is that it introduced extraneous noise into the system. Specifically, when data was collected to generate a slice within the field of view of one of the coils, the other coil was active and received noise or extraneous signals that were superimposed on the signals from the one coil.
One method to avoid summing the output of plural surface coils, was to provide a manual switch for selecting only a single coil to be active at a time. See for example, "Faraday Shielded Switchable Surface Coils Arrays", Molyneaux, et al., SMRI, 1989 Meeting Program and Abstracts, Abstract No. 340, Jul. 1989, U.S. Pat. No. 4,924,868 to Krause, et al.
Automated switching was suggested in "Switched Array Coils", Requardt, et al., Magnetic Resonance in Medicine, Volume 13, pages 385-397, (1990). One of the disadvantages of the Requardt system is that it utilized a hardware card with fixed precoding. Coil and sequence information were hard coded on the card. Modification of the machine was also required. Another disadvantage of this scheme resided in its lack of flexibility. The user was not allowed to define where to put slices, what type of imaging sequences to be run, and the nature of the coils to be used. No provision was made for user parameter selection. Second, the Requardt, et al. system performed the disclosed imaging operations alone, not in conjunction with a conventional whole body coil. The inability to activate the whole body coil rendered it difficult to determine the exact position of the coils and resultant images relative to the whole patient.
The present invention contemplates a new and improved computerized coil switching arrangement which overcomes the above-referenced problems and others.